chemical engineering MCQs – Page 206

Practise multiple-choice questions from chemical engineering for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

chemical engineering Mcqs
4101. According to Reynolds analogy, Stanton number is equal to (where, f = Fanning friction factor) ?
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A. 2f

B. f/2

C. f

D. f/4

4102. Heat flux is the time rate of heat transfer per unit_______________?
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A. Area

B. None of these

C. Length

D. Volume

4103. Economy of an evaporator is influenced by the_____________________?
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A. Steam pressure

B. Feed temperature

C. Number of effect

D. Both B. & C.
4104. Low thermal conductivity of heat insulating materials is due to its_________________?
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A. None of these

B. High specific heat

C. Dense structure

D. High proportion of air space
4105. The rate of heat transfer is a product of overall heat transfer co-efficient, the difference in temperature and the___________________?
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A. Heating volume

B. None of these

C. Nusselt number

D. Heat transfer area
4106. Increasing the liquor level in the evaporator results in the_______________?
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A. Decreased effect of hydrostatic head

B. Decreased capacity

C. Increased true temperature drop

D. Increase in liquor film co-efficient

4107. Black liquor generated during paper manufacture is concentrated in a___________________?
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A. Multiple effect evaporator

B. Single effect evaporator

C. Single effect evaporator followed by a crystalliser

D. Multiple effect evaporators followed by a crystalliser

4108. Heat transfer efficiency leading of energy conservation in a heat exchanger can be achieved by____________________?
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A. Increasing the tube length

B. Enhancing the fluid pumping rate

C. None of these

D. Keeping the heat transfer surface clean
4109. The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K = 0.04 W/m.K and thickness 0.16m is 10 W/m2. The temperature of the inside wall is 5C. The outside wall temperature is___________________?
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A. 40C

B. 25C

C. 30C

D. 35C
4110. Which of the following is unimportant in forced convection ?
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A. Reynolds number

B. Prandtl number

C. Grashoff number

D. None of these

4111. For a counter current heat exchanger with Ti h = 80C, Tc = 60C, Th = 50C and Ti c = 30C, and the temperature difference between the two streams being the same everywhere along Z, the direction of flow of hot fluid. The temperature profile should satisfy___________________?
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A. d2T/dZ2 > 0

B. d2T/dZ2 < 0

C. dT/dZ = 0

D. d2T/dZ2 = 0
4112. Low thermal conductivity of heat insulating materials is due to its_______________?
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A. High specific heat

B. None of these

C. Dense structure

D. High proportion of air space
4113. Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be_________________?
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A. 0.35

B. 0.45

C. 0.85

D. 0.55

4114. In case of a vertical tube evaporator, with increase in the liquor level, the ____________ is increased?
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A. Velocity of circulation

B. Liquor-film co-efficient

C. Both A. and B.

D. Neither A. and B.
4115. In regenerative air preheater (as practised in heating of coke ovens), the heat is transferred_________________?
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A. material</strong>

B. Through a metallic wall

C. None of these

D. By heating an intermediate material (like chequor bricks) and then heating the air from this

E. By direct contact of hot flue gas with air

4116. The number of kg vaporised per kg of steam fed to the evaporator is defined as____________?
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A. Economy

B. Rate of evaporation

C. Capacity

D. Rate of vaporisation

4117. Thickness of thermal boundary layer is more compared to that of hydrodynamic boundary layer, when the value of Prandtl number is_________________?
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A. > 1

B. 1

C. > 5

D. < 1
4118. Crystal size in a continuous crystalliser depends upon the___________________?
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A. All A., B. and C

B. Degree of turbulence

C. Rate of heat transfer

D. Degree of super-saturation

4119. A hollow sphere and a solid sphere of the same material and equal radii are heated to the same temperature. In this case ?
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A. The cooling rate will be the same for the two spheres and hence the two spheres will have

B. al temperatures at any instant

C. Both the spheres will emit equal amount of radiation per unit time in the beginning

D. Both will absorb equal amount of radiation from the surrounding in the beginning

E. Both B. & C.
4120. The heat flux in the nucleate boiling regimes is proportional to (where, ?T = excess temperature) ?
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A. ?(?T)

B. (?T)4

C. (?T)2

D. (?T)3